Tuesday, 28 June 2016

An excess of ADHD among children born to glyphosate appliers?

The job of pesticide applicator is one that has been discussed on this blog before (see here). Minus any scaremongering, the conclusion of that post was that under certain circumstances (e.g. a high pesticide exposure event - HPEE), the effects of that particular occupation might be pretty far-reaching for the 'cognitive' as well as physical health of the individual concerned.

Today I'm talking about other potential effects "needing confirmation by further studies" related to perhaps one of the most famous pesticides in recent times: glyphosate. The systematic review "of observational studies" by Jessica de Araujo and colleagues [1] (open-access) provides the starting material and the suggestion that whilst "exposures to GLY [glyphosate] before conception and/or during pregnancy did not increase the risk of adverse reproductive outcomes" there was perhaps more to see when it came to "an excess of risk of ADD/ADHD [attention-deficit disorder/attention-deficit hyperactivity disorder] among the offspring of GLY applicators." The de Araujo paper was a review paper and included the findings reported by Vincent Garry and colleagues [2] that: "Use of the herbicide glyphosate yielded an OR [odds ratio] of 3.6 (CI, 1.3-9.6) in the neurobehavioral category" including ADD/ADHD.

Before going back to the de Araujo and Garry papers, I think it's worth mentioning that the idea of an 'association' between GLY and ADHD is not without some controversy. I note that at least one attempt has been made to talk about the possibility of a link between the two albeit retracted for various methodological reasons. I therefore tread carefully and note there are some important strengths and weaknesses attached to the idea that offspring ADD/ADHD might specifically be more frequently present in GLY pesticide applicators.

Weaknesses, well, Garry et al relied heavily on self-report and interviews with no detailed use of analytical measures in terms of biological load for GLY. Yes, they did survey registered pesticide applicators on the basis of their licencing and the data provided at interview was cross-referenced with other available "medical records examination" but theirs was still a study heavily reliant on recall and association. de Araujo also make the point that "the herbicide was analyzed as a dichotomous (exposed / not exposed) variable" which takes no account of variables such as "wearing protective clothes, the diet, the amount of the pesticide used" and thus, says nothing about any dose-response relationship. Strengths - the Garry paper did cover various different types of pesticides, the metabolites of some have also subsequently been linked to risk of a diagnosis of ADHD for example (see here). They also reported on quite a few other variables that might impact on risk of offspring ADHD and controlled for them. In short, an interesting association which again is: "needing confirmation by further studies."

Insofar as the possibility that there may 'associations' between glyphosate use and behavioural outcomes, some people with some knowledge of autism research might have come across some pretty stark warnings about glyphosate exposure and the quite staggering increase in cases of autism being diagnosed around the world (see here). I, myself, am not so convinced that one agent, and one agent alone, plays such an important role in autism rates but am willing to concede that there may be more research to do on the effects of exposure and offspring outcomes (see here). Indeed minus any sweeping generalisations or solely resting any 'blame' at the door of a specific preparation, science really needs to conduct some more detailed analysis on environmental components such as pesticides and behaviour and developmental outcomes (including biochemistry [3]), if anything else, just to rule out any relationship. And various lawmakers around the world might be aiding efforts to do so...

[2] Garry VF. et al. Birth defects, season of conception, and sex of children born to pesticide applicators living in the Red River Valley of Minnesota, USA. Environmental Health Perspectives. 2002;110(Suppl 3):441-449.

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Questioning Answers

About Me

I have been involved in autism research for more years than I care to remember. My Questioning Answers blog (http://questioning-answers.blogspot.com/) is a place to describe and discuss various research into autism spectrum and related conditions. My Gutness Gracious Me blog (http://gutness-gracious-me.blogspot.com/) is for discussions on various gastrointestinal research. I make no recommendations, I am not giving any medical advice, I am not formulating any specific opinions and do not want to get into any ethical, political or religious debates. I am not trying to change anyone's opinions, views, beliefs or anything else. These are purely blogs about science and research in autism and a few other interesting things. Any posts I make are my own opinions and not reflective of any organisation I am affiliated to. Keep in mind that science deals with probabilities not absolutes.

ABOUT AUTISM SPECTRUM CONDITIONS

Autism or autism spectrum conditions describe several presentations characterised by core issues with social affect and stereotyped or repetitive actions. Diagnosis is made by observation and analysis of developmental history. These are heterogeneous conditions which can carry various co-morbidities and whilst described as life-long are affected by age and maturation. Autism means different things to different people. To some it means a need for life-long support. To others it is part of the varied tapestry of humanity. To all it means a need to foster a welcoming society with appropriate support and opportunities.